Bit mouthpiece
The mouthpiece is the part of a horse's bit that goes into the mouth of a horse, resting on the bars of the mouth in the sensitive interdental space where there are no teeth. The mouthpiece is possibly the most important determinant in the severity and action of the bit. Some mouthpieces are not allowed in dressage competition.
The other parts of the bit are the bit rings on a snaffle bit, and the shanks on a curb bit. These pieces do not go inside the mouth, but rather are the parts of a bit that are outside the mouth, where the bridle and reins attach.
Design concepts
Particular mouthpieces do not define the type of bit. Often, bits with mouthpieces, such as single or double-jointed bits, are incorrectly referred to as snaffles, which in actuality refers to a direct action bit, rather than a leverage bit, and not the mouthpiece. Though some mouthpieces are marked as "severe" and others as "mild", this is all relative. A heavy-handed rider can make even the mildest bit uncomfortable, and a skilled, light rider can ride in a much harsher mouthpiece without damaging the mouth or causing any distress in the horse. Additionally, the type of bit has a great impact on the action of the mouthpiece. Snaffles are generally considered the mildest, curbs and gags the harshest. It is difficult, therefore, to compare a harsher-type bit with a mild mouthpiece, and a milder-type bit with a harsher mouthpiece. In general, however, the mouthpiece can have a marked difference on the severity. Snaffles with twisted wires are never considered mild, while a pelham with a low port may. In short, many factors in the bitting equation must be considered to evaluate the action and severity of a bit.Various types of metal or synthetic substances are used for bit mouthpieces, which may determine how much a horse salivates or otherwise tolerates a bit; a horse having a moist mouth is considered more relaxed and responsive. Commonly used metals include stainless steel and nickel alloys, which generally do not rust and have a neutral effect on salivation; sweet iron, aurigan and copper, which generally tend to encourage salivation; and aluminum, which is considered drying and is discouraged as a mouthpiece metal. Synthetic mouthpieces may be made with or without internal metal cable or bar reinforcement. Rubber bits are generally thicker than metal bits, but other types of plastics are also used, often the same size and some flavored.
Bits without joints
Straight-bar and Mullen mouth
Types of Bits: All types.What it is: The mouthpiece is a straight bar of material, without any joints or ports. In the mullen mouth, the bar has a slight bow to it, curving gently to allow some room for the tongue.
Action: The mullen mouth and straight bar are fairly similar in action, placing pressure on the tongue, lips, and bars. The mullen provides extra space for the tongue, instead of constantly pushing into it, resulting in more tongue relief, and making it more comfortable, but the mullen does not have as high of a port as a curb, thus does not offer full tongue relief. This bit is generally considered a very mild mouthpiece, although this varies according to the type of bit leverage, and improper use may make it harsh, since the majority of the bit pressure is applied on the sensitive tongue.
Materials: Rubber is very common, as are other synthetic materials. Stainless steel is also a favorite, but copper and sweet iron are not as popular.
Uses: Seen in all equestrian activities, although less commonly in dressage. Usually not as popular for snaffles or gags as for bits that use leverage. The straight bar is common in stallion in-hand bits.
Variants: A variant that is somewhat between the mullen and a low port, seen primarily in western riding is called a "sweetwater" bit and is a very wide, low port slightly more arched than a mullen that offers full tongue relief, puts pressure only on the bars, and is primarily used as a curb mouthpiece. Spade and "half-breed bits also have a straight bar mouthpiece, but with the addition of a port, spoon, or other accoutrements, and thus are not truly classified as a mullen or straight bar mouthpiece."
Ported
Types of Bits: All types, including driving bits.What it is: The middle of the mouthpiece has a "port," or curve, which may vary in size from "low" to "high." The port is different from the mullen mouth in that the curved portion does not extend the width of the mouthpiece, but is only an inch or two in the center of the bar.
Action: Ported bits act on the lips, tongue, and roof of the mouth, and may apply extra pressure to the bars. The action of the port is directly related to its size. Low ports provide some tongue relief, similar to the mullen mouth, as they provide more space. Larger ports press on the hard palate when the reins are pulled, act as a fulcrum, and transfer that pressure onto the bars. Recent research has shown that the port must be 2-2.5" or more in height before it touches the hard palate. Thus the mildest port height is not necessarily the lowest ported bit, as commonly believed; it can also be the highest port possible that does not contact the hard palate.
Materials: Always metal, often stainless steel but also may be sweet iron or copper.
Uses: Very uncommon in snaffles and gags. One of the most common mouthpieces in pelhams, Kimblewick, and curbs. Very popular in the Western disciplines.
Jointed/single-jointed
Type of Bits: Very common on snaffle bits, but seen on all bit families including Kimblewicks, pelhams, gags, and curbs.What it is: The mouthpiece has one joint in its center. It "breaks" upward toward the top of the mouth with direct pressure, and outward toward the front of the mouth when used with leverage pressure from a bit shank.
Action: The single-jointed mouthpiece applies pressure to the tongue, lips, and bars. Due to the V-shape of the bit when the mouthpiece is contracted, it causes a "nutcracker" action, which has a pinching effect on the bars. It also causes the joint of the bit to push into the sensitive roof of the mouth if used harshly. A single-jointed bit with a curved mouthpiece has a more "U" shape which tends to decrease the pressure on the roof of the mouth.
Materials: often stainless steel, but may be made of any bit metal, happy mouth material, or have a rubber covering on each joint.
Uses: This is one of the most common mouthpieces found on a snaffle, and is popular for all equestrian sports.
Cautions: Curb bits with a single joint are often called cowboy snaffle, Argentine snaffle, or Tom Thumb snaffle. However, these bits all are actually curb bits because they have shanks and operate with leverage. Thus, when the reins are pulled, the horse is subjected both to the nutcracker action of the jointed mouthpiece and the leverage of the curb, which also causes the jointed bit to rotate and press into the tongue. Therefore, such bits can be very harsh, particularly in the hands of an inexperienced rider. Adding a solid "slobber bar" at the end of the shanks may reduce, but does not eliminate, this problem.
Double jointed bits
Double-jointed bits reduce the nutcracker effect because they conform better to the horse's U-shaped mouth, instead of the "V" created by a single joint. In this respect they are milder, and many horses prefer a double-joint over a single joint.Many of the double-jointed bits are occasionally "added to" by twisting the cannons of the mouthpiece. This increases the severity of the bit, as these cannons act directly on the tongue and bars in addition to the regular action of the bit. A relatively "kind" French mouth can therefore be turned into a severe bit when the cannons are twisted or if the mouthpiece is put onto a gag bit. All references below are based on the cannons being smooth, not twisted.
The French mouth/ French link
Types of Bits: snaffle, gag, pelham, curbWhat it is: The mouthpiece has two joints due to a central link. This link is usually flat, short and has bone-shaped, rounded corners. Some French link snaffles are not flat, but are rounded in the same manner as the rest of the mouthpiece. The flat link is mild when it lays flat across the tongue, but the edge can put pressure on the tongue if a full-cheek version with keepers places the link at an angle. A rounded link does not have this action
Action: One of the mildest mouthpieces, because the two joints reduce the nutcracker effect found in single-jointed bits, and encourage relaxation—applies pressure to the lips, tongue, and bars of the mouth
Materials: Usually stainless steel, also copper
Use: Commonly seen on snaffles, rare in gags, pelhams, or curbs. This is one of the most popular mouthpieces for dressage work. However, it is used in many English-styled disciplines. It is rarely used in the Western-styled disciplines.
The Dr. Bristol
Types of Bits: snaffle, gagWhat it is: The mouthpiece has two joints due to a central link. This link is flat, but longer and more rectangular in shape than a French link. It is also usually set at a slight angle to the plane of the bit. Its inventor, J.S. Bristol, was purported to have been a dentist.
Action: The double joint reduces the nutcracker effect found in single-jointed snaffles. However, the middle link is angled relative to the side pieces of the bit. As a result, the thin edge of the center link can press into the tongue, creating a very small bearing surface. When a full-cheek Dr. Bristol is used, the bit can be rotated so that the angled middle joint lies flat with its broad side against the tongue; when used this way the bit is relatively mild. This latter method is only possible because bit keepers ensure the bit stays in a fixed position in the horse's mouth, and thus bits that do not use bit keepers do not have this milder option.
This bit can put pressure on the tongue, although it also adds pressure to the bars and lips of the mouth. It contains a double jointed mouthpiece similar to the French link, with the center section a flat plate. In its original form, the plate was intended to lie across the whole width of the horse's tongue. Bristol insisted that this bit was intended to be comfortable for the horse because the central plate would lie flat onto the tongue thus lowering the pressure.
The action has been a topic of controversy with many popular texts describing it as having a harsh action due to the plate's edge orientation to the tongue. Academic research has clarified these claims, showing that harsh action occurs when the bit is placed into the mouth such that the feature angle, as defined from a left hand side view, is +45 °. In this sense the bit might be used in two different ways, one such that the plate lies flat to the tongue and is 'mild' and the other such that the plate lies edge-on to the tongue and is 'harsh'.r.
Materials: Usually stainless steel, also copper.
Use: Commonly seen on snaffles, very rare in gags. This bit is seen in many of the English disciplines, but is not used in Western disciplines. Rare in dressage due to its potential severity. Legal for use in the United States, but often not allowed in sanctioned Dressage competition in other nations. Seen in many jumping disciplines.